The invention concerns a sample injection and extraction head, respectively, for gaseous or liquid fluids especially for the use in gas chromatography, more especially in capillary chromatography. Sample injection heads are especially used in septum-free cold sample injection, preferably in oncolumn mode, according to which a sample to be analyzed is injected into the chromatographic system.
From the German Patent No. 3.400.458 a septum-free sample injection head for the use in capillary gas chromatography is known which is provided with an inlet valve having a valve body being spring biased against a sealing ring. The valve body is a ball which upon insertion of a syringe needle is obliquely thrusted away against the spring bias and the syringe needle is introduced into the injection head through the sealing ring. However, the introduction through the sealing ring risks to damage the sealing ring. Furthermore, the sealing ring comes out of round by clamping it between the valve housing and the injection head so that the pressing force of the ball-like valve body has to be relatively great to ensure a continuous line contact of the ball-like valve body and the sealing ring. This makes the valve difficult to actuate. The adjustment of the ball and the valve housing which is to be provided with a passage for the syringe needle is also difficult to manage and a corresponding machining is necessary.